With the discovery of polymer chemistry the fabric and film industries were revolutionized. Although many useful man-made compositions were developed to improve the quality of life in general, the search for polymeric compositions with improved properties has been a continual one. It has long been recognized that polymeric products, particularly fibers, films, fabrics and molded articles, when subject to excessive heat or contact with open flame, could be improved by imparting flame retardant properties to such products. The art of treating polymers is replete with attempts to reduce the flammability of such products.
Approaches such as coating the article, adding a flame retardant compound during polymerization, or incorporating the retardant in the polymer after polymerization have been attempted with various levels of success.
Perhaps the most common approach to treating articles such as polymeric fibers, films and fabrics has been to coat the article with a substance that would render the article resistant to burning. Such coatings are often removed during the useful life of the article by being worn off or washed out.
Incorporating the flame retardant material into the article itself appears to hold the most promise for the future; however, this approach has often been unsucessful due to undesirable changes in the properties of the finished polymer as a result of the flame retardant additive.
It has been observed that the mechanical properties, such as tensil strength, or the color of polymer in which flame retardant is incorporated may be adversely affected. In certain cases compatibility of the flame retardant with the polymer may be affected by processing conditions. For example, normal heat treatment or dyeing of fibers may cause the flame retardant to migrate to the surface of the polymer, thereby reducing the acceptability, in commerce, of the treated fiber. In addition the presence of certain flame retardant compositions in the polymer may corrode or otherwise adversely affect equipment employed to spin or shape the polymer into useful forms.
It has now been discovered that oligomers of (substituted phenoxy)cyclotriphosphazenes and aromatic diols when incorporated into polymeric compositions render such compositions flame retardant without significant adverse effect on the useful properties of the polymeric compositions.
Polymeric cyclotriphosphazenes are described in U.S. Pat. No. 3,711,542.